keil c

#include "reg51.h"
void main(void)
{
  sbit P1_0=P1^0;
  sbit P2_0=P2^0;
}
error message如下
Build target 'Target 1'
compiling test.c...
TEST.C(4): error C141: syntax error near 'sbit'
TEST.C(4): error C202: 'P1_0': undefined identifier
TEST.C(5): error C141: syntax error near 'sbit'
TEST.C(5): error C202: 'P2_0': undefined identifier
Target not created
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我的問題是,為何sbit不能使用??
在reg51.h中,已經有宣告
sfr P1   = 0x90;
sfr P2   = 0xA0;
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